The invention relates to a two-stroke engine comprising a cylinder with a combustion chamber provided therein that is delimited by a piston. The piston drives in rotation a crankshaft that is rotatably supported in a crankcase. In at least one position of the piston, the crankcase is connected by means of at least one transfer passage with the combustion chamber. An outlet is provided at the combustion chamber. An air passage is provided as well as a mixture passage that opens with a mixture inlet into the cylinder bore and is piston-controlled by the piston. The transfer passage is connected in the area of top dead center of the piston by means of a piston recess to the air passage. The invention further relates to a hand-held power tool with such an engine.
U.S. Pat. No. 7,082,910 B2 discloses a two-stroke engine comprising an air passage and a mixture passage. By means of the air passage scavenging air is supplied to the transfer passages through a piston recess. The scavenging air is supposed to separate the fresh mixture that is flowing from the crankcase into the combustion chamber from the exhaust gases in the combustion chamber that are flowing out through the outlet in order to thus reduce scavenging losses.
It has been found that two-stroke engines that operate with scavenging air may stall as engine speeds decrease under load.